Heretofore, tree treatment capsules consisting of a generally cylindrical hollow container and a plug for insertion into a pre-drilled hole in a tree to be treated have been known. Such tree treatment capsules have typically been made of a frangible material, or of a hard, brittle, breakable and non-elastic material, such as fiberglass, wood or wood fiber. However, the hollow containers of these known capsules tend to be breakable before they are assembled or even after assembly upon inadvertent application of an external impact.
Tree treatment capsules made of a brittle, breakable plastic material are also known. However, although it is difficult to break such capsules before usage, it is also difficult to break them when they are in use. Consequently, a great deal of force must be applied to provide a large enough impact to cause the capsule to break.